In a good conductor, the energy gap between the conduction band and the valence band is
1. Infinite
2. Wide
3. Narrow
4. Zero

A Ge specimen is doped with Al. The concentration of acceptor atoms is $~{10}^{21}$ $\mathrm{atoms}/{\mathrm{m}}^3$. Given that the intrinsic concentration of electron hole pairs is $~{10}^{19}/{\mathrm{m}}^3$, the concentration of electrons in the specimen is:

In a semiconducting material, the mobilities of electrons and holes are ${\mathrm{\mu }}_{\mathrm{e}}$ and ${\mathrm{\mu }}_{\mathrm{h}}$ respectively. Which of the following is true?
1. \(\mu_{e} > \mu _{h}\)
2. \(\mu_{e} < \mu _{h}\)
3. \(\mu_{e} = \mu _{h}\)
4. \(\mu_{e} <0; ~\mu _{h}>0\)

The diode used in the circuit shown in the figure has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milliwatts. What should be the value of the resistor R, connected in series with the diode for obtaining maximum current?

1. 1.5 $\mathrm{\Omega }$ 

2. 5 $\mathrm{\Omega }$

3. 6.67 $\mathrm{\Omega }$

4. 200 $\mathrm{\Omega }$

For the transistor circuit shown below, if $\mathrm{\beta }$ = 100, the voltage drop between emitter and base is 0.7 V, then the value of ${\mathrm{V}}_{\mathrm{CE}}$ will be:
                  
1. 10 V
2. 5 V
3. 13 V
4. 0 V

The figure shows two NAND gates followed by a NOR gate. Which of the following logic gate does the figure represent?

1. OR

2. AND

3. NAND

4. None of these

The diagram of a logic circuit is given below. The output F of the circuit is represented by:
       

1. W(X+Y)

2. W.(X.Y)

3. W+(X.Y)

4. W+(X+Y)

How much is the forbidden gap (approximately) in the energy bands of germanium at room temperature? 
1. \(1.1~\text{eV}\)
2. \(0.1~\text{eV}\)
3. \(0.67~\text{eV}\)
4. \(6.7~\text{eV}\)

Which of the following logic gate is a universal gate?

1. OR                       

2. NOT

3. AND                     

4. NOR

Consider an NPN transistor amplifier in the common-emitter configuration. The current gain of the transistor is 100. If the collector current changes by 1 mA, what will be the change in emitter current?
1. 1.1 mA                     

2. 1.01 mA

3. 0.01 mA                   

4. 10 mA